• Journal of the Korean Chemical Society
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• v.44 no.1
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• pp.10-16
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• 2000

In general, acid rain is unbuffered solution with low ionic strength and high resistance. Therefore during the pH measurement of acid rain, error can be occurred due to the liquid junction potential difference between the sample and the standard solution. Actually the average conductivity of rain in Taeduk Science Town during 1998 is 12.8 ${\mu}S/cm$, while that of pH standmd solutions is about 5,980 ${\mu}S/cm$. There is a large difference in ionic strength. To compensate the bias due to residual liquid junction potentials, a quality control standard(QCS) of dilute sulfuric acid, which has the conductivity and pH values simikw to rain, was prepared. The pH of QCS solution was determined using the hydrogen electrode system without liquid junction, and compensation has been made for the bias terms by performing the pH measurements with glass electrode. On the basis of this compensation method, the pH vaiues of rain in Taeduk Science Town during 1998 were measured.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.02a
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• pp.245-256
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• 2004

The extraction of three kinds of amido podands, N,N,N'N'-tetrabutyl-3-oxa-pentanedi- amide (TBDGA), N,N,N'N'-tetra-isobutyl-3-oxa-pentanediamide(TiBDGA) and N,N,N'N'-tetra- butyl-3,6-dioxa-oct-anediam- ide(TBDOODA) on U(VI),Pu(IV), Am(III), Eu(III) and other metal ions is studied in nitric acid solutions. 40%octanol-kerosene is chosen as diluents to eliminate third phase and emulsion. TBDGA and TiBDGA show extraction selectivity to An(III) and Ln(III) much higher than to U(VI) and Pu(IV). Fe, Ru and Mo is poorly extracted by the three kinds of amid podands in 2~3mol/L $HNO_3$ solutions. Aiming to eliminate interface crude when using simulated HLLW solution in the system of 0.2mol/L TBDGA/Octanol＋kerosene, acetohydroxyamic acid was adapted. Distribution ratio of zirconium was decreased when adding acetohydroxyamic acid in aqueous solution, and interface crude disappeared as mixing extractant with HLLW. The counter-current extraction test is carried out in a set of miniature mixer-settler, with 0.2mol/L TBDGA/ 40% octanol-kerosene as extractant to separate U(VI), Pu(IV), Am(III) and Eu(III) from simulated high level liquid waste(HLLW) solution. In battery A, lanthanides and actinides are coextracted into organic phase with the recovery of 99.98% for U(Ⅵ), >99.99% for Pu(IV), and >99.99% for Am(III) and Eu(III) respectively. In battery R1, 99.99% U, 86.2% Pu and a part of Am or Eu are stripped into aqueous phase by 0.2mol/L acetohydroxyamic acid (AHA) in 0.01mol/L $HNO_3$ solution. In battery $R_2$, Am, Eu and remained Pu are completely back-extracted by 0.2mol/L AHA. This separation process contains no salt reagent, and it is not necessary to dilute HLLW feed.

• KSBB Journal
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• v.11 no.4
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• pp.481-488
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• 1996

In spite of diverse applications of chitin derivatives, commercial use of chitin has been limited due to highly resistance to chemicals and the absense of proper solvents. One of methods to reduce such high resistance to chemicals is to make microcrystalline chitin(MCC) by hydrolysis of chitin. Presently, MCC is produced mainly by using high concentration of acid, but this treatment requires an extensive posttreatment to remove or recover acid. An alternative process for MCC production was developed by using dilute hydrochloric acid with ultrasound and hydrogen peroxide. The major parameters for this process were found to be acid concentration, swelling time and temperature, and irradiation time and frequency of ultrasound. The effects of these parameters on MCC molecular weight were investigated. The molecular weight of MCC produced at a typical condition was around 30,000 which was approximately 1/8 of that of chitin and approached to a constant value. This phenomenon was explained by introducing the model of molecular arrangement of cellulose. SEM analysis showed that both chitin and MCC had a fibrous shaped morphology and the fibril size of MCC was much smaller than that of chitin.

• Journal of the Korean Electrochemical Society
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• v.12 no.1
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• pp.34-39
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• 2009

In this study, a needle coke was oxidized in a mixture of dilute nitric acid and sodium chlorate ($NaClO_3$) solutions and followed by heat treatment. The samples were analyzed with using XRD, FESEM, elemental analyzer, BET, and Raman spectroscopy. Double layer capacitance was measured with the charge and discharge measurements. The consisting layers of the needle coke were expanded to single phase showing only (001) diffraction peak by the acid treatment for 24 hours. The oxidized coke returned to a graphite structure appearing (002) peak after heat treatment above $200^{\circ}C$. The structure returned could be more easily accessible to the ions by the first charge, and improve the double layer capacitance at the second charge. The two-electorde cell from acid treated coke and $300^{\circ}C$ heat treatment exhibited the maximum capacitances of 32.1 F/g and 29.5 F/ml at the potential of $0{\sim}2.5\;V$.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.114.2-114.2
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• 2011

Furfural is a versatile derivative. It can be utilized for a building-block of furfuryl alcohol production and a component of fuels or liquid alkanes. But in bio-process, furfural is a critical compound because it inhibits cell growth and metabolism. Furfural could be converted from xylose and usually produced from biomass in which hemicellulose is abundant. In this study, furfural production from miscanthus was performed and utilization of miscanthus residue was consequently conducted. At first, hydrolysis for investigation of miscanthus composition and furfural production was performed using sulfuric acid. Previously, we optimized dilute acid pretreatment condition for miscanthus pretreatment and the condition was found to be about 15 min of reaction time, 1.5% of acid concentration and about $140^{\circ}C$ of temperature and 60% (about 7 g/L) of xylose was solubilized from miscanthus. Using the xylose, furfural production was conducted as second step. Approximately $160{\sim}200^{\circ}C$ of temperature was accompanied with the hydrolysis for pyrolysis of biomass. When the investigated condition; $180^{\circ}C$ of temperature, 20 min of reaction time and 2% of acid concentration was operated for furfural production, furfural productivity was reached to be 77% of theoretical maximum. After reaction, residue of miscanthus was utilized as feedstock of ethanol fermentation. Residue was well washed using water and saccharified using hydrolysis enzymes. Hydrolysate (glucose) from saccharification was utilized for the carbon source of Saccharomyces cervisiae K35.

• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.802-808
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• 1996

Silicic acid(SA) was extracted with organic solvents from aqueous sodium silicate solutions acidified with dilute sulfuric acid. Tetrahydrofuran(THF), isopropyl alcohol and acetone were used as organic solvents. The extraction degree of Si and the removal efficiency of Na is determined according to kinds of solvent and the mixing ratios of solvent, sodium chloride and $H_2O$. Optimum conditions for the preparation of high purity SA were THF as an organic solvent, volume ratio of organic solvent/SA : 1 (organic solvent 10ml/10ml SA) and the amount of NaCl addition 2.5g/10ml SA. The extraction degree of Si and the removal efficiency of Na at that point were 86.2% and 99.95% respectively and the purity of SA was 99.96%.

• Korean Journal of Food Science and Technology
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• v.27 no.3
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• pp.286-289
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• 1995

To find composition of white crystals in canned bamboo shoots, the solubility in distilled water or dilute HCl solution, organic acid composition, mineral composition and amino acid composition of white crystals were analyzed. The contents of ash, protein, fat and carbohydrate were 55.12%, 14.21%, 0.70% and 29.97% respectively. Only oxalic acid was detected by HPLC analysis as an organic acid. Judging from solubility of white crystals, the type of salt was Ca-oxalate. The content of calcium was 72.68% in total amount of minerals. The content of tyrosine was 75.23% in total amount of protein. In conclusion, white crystals was constituted by Ca-oxalate and tyrosine complex.

• Korean Journal of Environmental Agriculture
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• v.15 no.1
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• pp.1-10
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• 1996

The contents of heavy metals in soil near the Janghang smelter area were observed to understand present status and relationship between their fraction and the absorption by rice. The soil samples were taken from the eight sites of the paddy fields in 1982 and 1990, and analysis on heavy metals including Cd, Zn, Cu and Pb was performed. The results were as follows: Total contents of heavy metals in the samples of 1990 were higher than those of 1982. The order of increasing ratio was Cu > Zn > Pb > Cd and the variation of Cd content by sequential differente extracting was residual > exchangeable > dilute acid-extractable fractions and its increasing range was from 38 to 71% during nine years. The ratio of immobile heavy metals bound within an oxide or silicate matrix of Fe-Mn oxide bound and residual in surface soil was that Cd, Pb, Cu and Zn were 31.65, 42.22, 76.57 and 79.49%, respectively, and their mobile ratios of exchangeable, dilute acid-extractable and organically bound were more than 20.28%. Those of mobile Cd, Pb, Cu and Zn were 68.35, 55.78, 23.43 and 20.28%, respectively. Correlation between the heavy metal contents in surface soil and those in tissue of rice plant, such as leaf blade, leaf sheath, stem and panicle axis, were significant, but were not significant in subsurface soil. The dilute acid-extractable and organically bound fractions of Cd, Cu, Pb and Zn in surface soil were more significantly correlated with those in tissues of paddy rice.

• Korean Journal of Environmental Agriculture
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• v.15 no.3
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• pp.372-382
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• 1996

In order to elucidate the relationship between the mobility of heavy metals in soil and their uptake by plants, the soil samples collected from the Mangyeong River area were analyzed for the contents and existing forms of the heavy metals and the correlation between the contents of heavy metals in the soil and those in various parts of rice plants therefrom. The soil samples were collectes from ten sites in the paddy fields in 1982 and 1990, respectively, and the analysis on heavy metals including Cd, Zn, Cu and Pb was performed. The results are as follows: Total contents of heavy metals in the samples of 1990 were higher than those of 1982. The extent of increase was that Cd, Zn, Cu and Pb were 3, 29, 59 and 8% in top soil and 8, 50, 91 and 8% in sub-soil, respectively. The order of increasing ratio was Cu > Zn > Pb > Cd and the variation of Cd content by sequentially different extraction was organically bound > dilute acid-extractable=Fe-Mn oxide bound > exchangeable > residual fractions and the content of Cd with organically bound was $46.62{\sim}48.08$ and $41.18{\sim}50.18%$ of total Cd in top and sub-soil, respectively. The ratios of immobile heavy metals, Cd, Pb, Cu and Zn, bound within an oxide or silicate matrix of Fe-Mn oxide in top-soil were 21.25, 35.98, 74.18 and 82.12%, respectively, and consequently their mobile ratios of exchangeable, dilute acid-extractable and organically bound were more than 17.88%. Those of mobile Cd, Pb, Cu and Zn were 78.25, 64.02, 25.82 and 17.88%, respectively. Except for Pb a correlation between the contents of Cd, Zn, and Cu of exchangeable and dilute acid-extractable in top-soil and those in leaf blade, stem and panicle axis was significant, but was not significant in sub-soil.

• Resources Recycling
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• v.7 no.3
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• pp.17-26
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• 1998

A study on the recovery of silver and nitric acid in the liquid waste resulted from the mediated electrochemical oxidation(MEO) process was conducted. The removal of silver in the concentrated nitric acid solutions was carried out by the electrodeposition. The removal efficiency more than 98% could be obtained in nitric acid concentrations less than 3 M with the current efficiency of nearly 100%. The experimonts on the evaporation for the recovery of nitric acid were performed as well. At the evaporation factor of 25., the degree of nitric acid recovery in 3.5 M nitric acid solution containing 0.5 to 1.0 mol% NaNO, was 80~90% resulting in 2.8~3.1 M nitric acid. The design factors and operating conditions of the distillation tower were analyzed by using MEH model derived by Maphtali-Sandholm with the throughput of 4 kg/hr for the enrichment of dilute nitric acid solution recovered by evaporation to reuse in the MEO process. The distillation column composed of eleven theoretical stages having the overall tray efficiency of 70% are needed to obtain 1.03 kg/h of 12M nitric acid and 2.97 kg/h of water with feed being introduced to the column at tray 6 from the bottom at the reflux ratio of 0.25, the reboiler with the heat load of 2.7 kW, and the condenser with the cooling load of 0.5 kW.